Japanese Encephalitis Virus (JEV) infection in different vertebrates and its epidemiological significance: a Review

Abstract

The maintenance of Japanese Encephalitis Virus (JEV) in nature occurs in a cycle which includes mosquito vectors and the vertebrate hosts. Japanese encephalitis (JE) being primarily a zoonotic disease, animal hosts such as pigs and birds play an important role in the maintenance and amplification of the virus. JE antibody has been detected in several poikilothermic and homeothermic vertebrates, apart from the recognized reservoir/amplifying hosts. Emerging arboviral diseases such as Japanese Encephalitis, Chikungunya, Dengue generally stems from an animal reservoir, but there is inadequate information on the natural history of arboviruses especially its method of survival in the inter- epidemic period. Keeping in view the above perspective, an attempt has been made to review the various non-human vertebrates infected with JEV and to analyze their epidemiological significance. Some zoonotic potential might exist in the ectothermic animals as overwintering reservoir hosts for Japanese Encephalitis Virus (JEV). Mosquito species having predilection to animal blood could get the virus from a broad array of low viraemic ectothermic and endothermic vertebrates, but possibly fail to attain the infective stage and to acquire transmission competence due to inadequate titre level and short duration of viraemia in those vertebrates. These animals might have some complementary role in the maintenance of the enzootic cycle of the virus along with the recognized principal reservoir hosts i.e., pigs and birds. The principal and complementary vertebrate reservoir hosts keep the virus circulating perennially in nature and epizootic occurs at the time of higher than average level of virus circulation.